# Feedback

• At one point, you used ${\displaystyle q_{i}}$ and ${\displaystyle p_{u}}$ to describe the latent features, then changed it to ${\displaystyle f_{i}}$ and ${\displaystyle g_{u}}$.
${\displaystyle (\sum _{\in D}(r^{'}+b_{i}+c_{u}+(\sum _{\overline {s}}f_{ik}g_{ku})-r)^{2})+(\lambda (b_{i}^{2}+c_{u}^{2}+\sum _{k}(f_{ik}^{2}+g_{ku}^{2})))}$
Then where are the indices ${\displaystyle i}$ and ${\displaystyle u}$ for the second term coming from...? What is the outermost bracket supposed to mean?